threadpool: log error on thread creation failure and catch exception

Change-Id: I9bd038fd1306d11f752618221f419a2d551ebc2f
Reviewed-on: http://gerrit.aldebaran.lan:8080/17799
Reviewed-by: proullon <proullon@aldebaran-robotics.com>
Reviewed-by: mnottale <mnottale@aldebaran-robotics.com>
Tested-by: llec <llec@aldebaran-robotics.com>